Taxonomy "under construction": advances in the systematics of Apocynaceae, with emphasis on the Brazilian Asclepiadoideae

Analysis of the Volatile and Enantiomeric Compounds Emitted by Plumeria rubra L. Flowers Using HS-SPME-GC

The volatile components emitted by fresh aromatic flowers of Plumeria rubra L., harvested in southern Ecuador during three different months were determined to evaluate the fluctuation of secondary metabolites. The volatile compounds were analyzed using headspace solid-phase microextraction (HS-SPME) followed by gas chromatography coupled to mass spectrometry (GC-MS) and a flame ionization detector (GC-FID) using two types of columns: a non-polar (DB-5ms) and polar column (HP-INNOWax). The principal chemical groups were hydrocarbon sesquiterpenes (43.5%; 40.0%), oxygenated sesquiterpenes (23.4%; 26.4%), oxygenated monoterpenes (14.0%; 11.2%), and hydrocarbon monoterpenes (12.7%; 9.3%). The most representative constituents were (E,E)-α-Farnesene (40.9-41.2%; 38.5-50.6%), (E)-nerolidol (21.4-32.6%; 23.2-33.0%), (E)-β-ocimene (4.2-12.5%; 4.5-9.1%), (Z)-dihydro-apofarnesol (6.5-9.9%; 7.6-8.6%), linalool (5.6-8.3%; 3.3-7.8%), and perillene (3.1-5.9%; 3.0-3.2%) in DB-5ms and HP-INNOWax, respectively. Finally, we reported for the first time the enantiomeric distribution of P. rubra flowers, where the enantiomers (1R,5R)-(+)-α-pinene, (S)-(-)-limonene, (S)-(+)-Linalool, and (1S,2R,6R,7R,8R)-(+)-α-copaene were present as enantiomerically pure substances, whereas (S)-(+)-(E)-Nerolidol and (R)-(+)-(E)-Nerolidol were observed as scalemic mixtures. This study provides the first comprehensive and comparative aroma profile of Plumeria rubra cultivated in southern Ecuador and gave us a clue to the variability of P. rubra chemotypes depending on the harvesting time, which could be used for future quality control or applications in phytopharmaceutical and food industries.

Plants used traditionally as antimalarials in Latin America: Mining the tree of life for potential new medicines

ETHNOPHARMACOLOGICAL RELEVANCE

Malaria remains a serious and challenging disease. Traditional antimalarial medicines are largely based on plants, and ethnopharmacological research has inspired the development of antimalarial pharmaceuticals such as artemisinin. Antimalarial drug resistance is an increasing problem in Plasmodium species, and new therapeutic strategies to combat malaria are needed. Although the number of malaria cases has been decreasing in Latin America, malaria remains a significant threat in many regions. Local people in Latin America have been using numerous plant species to treat malaria, some of which have been scientifically studied, but many others have not.

AIM OF THE STUDY

Our principal objective is to harness ethnobotanical data on species used traditionally to treat malaria, combined with phylogenetic approaches, to understand how ethnobotany could help identify plant genera as potential sources of new medicines.

MATERIALS AND METHODS

Plants used to treat malaria in Latin America were compiled from published and grey literature, unpublished data, and herbarium specimens. Initial assessment of potentially important species/genera/families included compiling the number of species used within the genus, the number of use reports per genus and species, and the geographic distribution of their use. The analysis of taxonomic distribution of species reported as antimalarial in Latin America (excluding the Southern Cone) was conducted, to determine which genera and families with reputed antimalarial properties are over-represented, and phylogenetic analyses were performed to identify if there was evidence for antimalarial species being dispersed/clustered throughout the tree or at its tips. This approach enabled 'hot-nodes' in certain families to be identified, to predict new genera with potential antimalarial properties.

RESULTS

Over 1000 plant species have been used to treat malaria in Latin America, of which over 600 species were cited only once. The genera with the highest number of antimalarial species were Aspidosperma, Solanum, Piper, Croton and Aristolochia. In terms of geographic distribution, the most widely used genera were Aspidosperma, Momordica, Cinchona, Senna and Stachytarpheta. Significant phylogenetic signal was detected in the distribution of native species used for malaria, analysed in a genus-level phylogenetic framework. The eudicot and magnoliidae lineages were over-represented, while monocots were not.

CONCLUSION

Analysis of ethnobotanical use reports in a phylogenetic framework reveals the existence of hot nodes for malaria across the Latin American flora. We demonstrate how species and genera currently lacking such reports could be pinpointed as of potential interest based on their evolutionary history. Extending this approach to other regions of the world and other diseases could accelerate the discovery of novel medicines and enhance healthcare in areas where new therapeutic strategies are needed.

Major Bioactive Alkaloids and Biological Activities of Tabernaemontana Species (Apocynaceae)

Several species belonging to the genus Tabernaemontana have been well researched and utilized for their wide-ranging biological activities. A few of the most prominent species include Tabernaemontana divaricata, Tabernaemontana catharinensis, Tabernaemontana crassa, and Tabernaemontana elegans. These species and many others within the genus often display pharmacological importance, which is habitually related to their chemical constituents. The secondary metabolites within the genus have demonstrated huge medicinal potential for the treatment of infections, pain, injuries, and various diseases. Regardless of the indispensable reports and properties displayed by Tabernaemontana spp., there remains a wide variety of plants that are yet to be considered or examined. Thus, an additional inclusive study on species within this genus is essential. The current review aimed to extensively analyze, collate, and describe an updated report of the current literature related to the major alkaloidal components and biological activities of species within the genus Tabernaemontana.

Flora of Ceará, Brazil: subtribe Gonolobinae (Asclepiadoideae/Apocynaceae)

Abstract We performed the taxonomic-floristic survey of subtribe Gonolobinae for the state of Ceará, as part of the “Flora do Ceará: knowing to conserve” project. The study was based on the comparative analysis of morphological characters, specialized bibliography, as well as photos of type-collections. In Ceará, six species of two genera were registered: Gonolobus rostratus, Matelea denticulata, M. endressiae, M. ganglinosa, M. harleyi, and M. nigra. Matelea ganglinosa has a broad distribution in the state, while G. rostratus, M. denticulata and M. endressiae are restricted. Matelea species were recorded in six Conservation Units and preferably dry environments (Stepic Savanna, Seasonal Deciduous Forest, and Lowland Semideciduous Forest).

Ruehssia quirinopolensis (Apocynaceae), a new species from the Cerrado Domain, Brazil

Abstract A new species of Apocynaceae, Ruehssia quirinopolensis, endemic to Serra da Confusão do Rio Preto and Serra da Igrejinha, Quirinópolis, state of Goiás, Brazil, is described and illustrated. It resembles R. rupestris, differing by the white corolla, adaxially villose and with a longer tube, and by its corona lobes with the upper portion lanceolate. Besides a distribution map for the new species, we provide a key to identify the nine species of Ruehssia that occur in Goiás. Ruehssia quirinopolensis is assessed here as Critically Endangered (CR).

Apocynaceae in the Atlantic Forest of Rio Grande do Norte, Brazil

Abstract We present here a taxonomic study of Apocynaceae from the Atlantic Forest remnants in the state of Rio Grande do Norte (RN), Northeast Brazil. Twenty-four species in 18 genera, distributed in Apocynoid grade (3 genera/5 species), Asclepiadoideae (8 genera/10 spp.), and Rauvolfioid grade (7 genera/9 spp.) were recorded. The most species-rich genera were Aspidosperma, Ditassa, and Mandevilla with three species each. The other genera were represented by one species each. Five genera and seven species were recorded in Rio Grande do Norte for the first time. Descriptions, identification key and comments on distribution and taxonomy of both genera and species are presented, as well as illustrations and figures.

Reproductive phenology of Ditassa burchellii (Apocynaceae, Asclepiadoideae), a herbaceous vine, in a semi-deciduous forest from Brazil

Abstract We analyzed the reproductive phenology of Ditassa burchellii and the influence of abiotic factors on the species phenophases. The study was conducted on individuals of a natural population from a semi-deciduous forest (Viçosa municipality, Minas Gerais state, southeastern Brazil). We quantified the activity and intensity indices of the following phenophases: flower bud, flower, immature fruit, and dehiscent fruit. To test for seasonality of phenophases, we analyzed each of them using Rayleigh test. We evaluated whether there was any association between abiotic variables (mean temperature, rainfall, and day length) and phenophases, in the month of occurrence and in the three months prior to the occurrence of each phenophase. The analyzed phenophases occurred mainly at the end of the rainy season and during the dry season, with overlapping periods, but with sequential peaks. The periods of occurrence of reproductive phenophases were similar to the ones in other climbing species and were mainly related to the dispersal mode. All phenophases were seasonal and were associated with at least one abiotic variable, either in the month of their occurrence or in the previous months.

Aspidosperma (Apocynaceae) no estado de Mato Grosso do Sul, Brasil

Resumo Aspidosperma compreende 55 espécies, das quais 41 ocorrem no Brasil. A maior riqueza está na região Centro-Oeste com 28 espécies. O presente trabalho teve como objetivo contribuir para o conhecimento da diversidade de Aspidosperma no Mato Grosso do Sul. Baseou-se na análise de amostras coletadas em 22 expedições de campo, visitas e consultas online aos herbários. No estado, o gênero está representado por 14 espécies. Aspidosperma quirandy e A. verbascifolium foram coletadas e descritas pela primeira vez no Mato Grosso do Sul. No presente estudo são apresentadas: chave de identificação para as espécies, descrição, distribuição geral e ecologia, dados de floração/frutificação, status de conservação e comentários taxonômicos.

Taxonomy of Aspidosperma Mart. (Apocynaceae, Rauvolfioideae) in the State of Pará, Northern Brazil

Aspidosperma Mart. is one of the most important genera from Apocynaceae Juss. occurring in Brazil. It is present in many plant formations and has species with both medicinal and economic value. From a taxonomic point of view, many of its species are difficult to identify, especially those occurring in the Amazonian region. In order to complement the information already available with regard to the taxonomy and distribution of the genus, the goal of this work was to provide a taxonomic study of the Aspidosperma species occurring in the state of Pará, northern Brazil. This study was based on the analysis of vouchers from the BHCB, HBRA, IAC, IAN, INPA, MG, R, RB and UEC herbaria, as well as scanned images of vouchers from Brazilian and foreign herbaria, and specimens collected in the field. Species identification was confirmed by analysis of protologues and types (or images). We present taxonomic descriptions, illustrations and one identification key for the 20 species of Aspidosperma found in Pará, with the Baixo Amazonas Mesoregion presenting the largest number of species (17), and the Metropolitana de Belém Mesoregion presenting the smallest number of species (3). Aspidosperma eteanum, A. oblongum, A. salgadense (endemic of Pará) and A. sandwithianum are accepted as species here. Aspidosperma cuspa is a new record for Pará. The fruits of Aspidosperma eteanum and A. salgadense, and the seeds of A. eteanum, have been described and illustrated for the first time.

Development and evolution of extreme synorganization in angiosperm flowers and diversity: a comparison of Apocynaceae and Orchidaceae

BACKGROUND AND AIMS

Apocynaceae and Orchidaceae are two angiosperm families with extreme flower synorganization. They are unrelated, the former in eudicots, the latter in monocots, but they converge in the formation of pollinia and pollinaria, which do not occur in any other angiosperm family, and for which extreme synorganization of floral organs is a precondition. In each family extensive studies on flower development and evolution have been performed; however, newer comparative studies focusing on flower synorganization and involving both families together are lacking.

SCOPE

For this study an extensive search through the morphological literature has been conducted. Based on this and my own studies on flowers in various Apocynaceae and Orchidaceae and complex flowers in other angiosperms with scanning electron microscopy and with microtome section series, a review on convergent floral traits in flower development and architecture in the two families is presented.

KEY FINDINGS

There is a tendency of protracted development of synorganized parts in Apocynaceae and Orchidaceae (development of synorganization of two or more organs begins earlier the more accentuated it is at anthesis). Synorganization (or complexity) also paves the way for novel structures. One of the most conspicuous such novel structures in Apocynaceae is the corona, which is not the product of synorganization of existing organs; however, it is probably enhanced by synorganization of other, existing, floral parts. In contrast to synorganized parts, the corona appears developmentally late.

CONCLUSIONS

Synorganization of floral organs may lead to a large number of convergences in clades that are only very distantly related. The convergences that have been highlighted in this comparative study should be developmentally investigated directly in parallel in future studies.

Tropical Refuges with Exceptionally High Phylogenetic Diversity Reveal Contrasting Phylogenetic Structures

Loss of phylogenetic diversity (PD) has gained increasing attention in conservation biology. However, PD is not equally distributed in a phylogeny and can be better assessed when species relatedness (phylogenetic structure: PS) is also considered. Here, we investigate PD and PS in two refuges of biodiversity in northeastern Brazil: the Bahia Costal Forest (BCF) in the Atlantic Forest domain and Chapada Diamantina (CD) in the Caatinga domain. We used geographic data of 205 species at two spatial scales and a chronogram of Apocynaceae based on matK sequences to estimate PD and PS. Our results show an exceptionally high PD in both refuges, overdispersed in BCF and clustered in CD, although this difference is less evident or absent for recent relationships, especially at a smaller spatial scale. Overall, PS suggests long-term competitive exclusion under climatic stability, currently balanced by habitat filtering, in BCF, and biome conservatism and limited dispersal leading to in situ diversification and high density of microendemics in CD. The phylogenetically clustered flora in CD, also threatened by climate changes, are naturally more vulnerable than BCF. Therefore, while in situ conservation may ensure protection of biodiversity in BCF, emergency ex situ conservation is strongly recommended in CD.

Phylogenetic signal detection from an ancient rapid radiation: Effects of noise reduction, long-branch attraction, and model selection in crown clade Apocynaceae

Crown clade Apocynaceae comprise seven primary lineages of lianas, shrubs, and herbs with a diversity of pollen aggregation morphologies including monads, tetrads, and pollinia, making them an ideal group for investigating the evolution and function of pollen packaging. Traditional molecular systematic approaches utilizing small amounts of sequence data have failed to resolve relationships along the spine of the crown clade, a likely ancient rapid radiation. The previous best estimate of the phylogeny was a five-way polytomy, leaving ambiguous the homology of aggregated pollen in two major lineages, the Periplocoideae, which possess pollen tetrads, and the milkweeds (Secamonoideae plus Asclepiadoideae), which possess pollinia. To assess whether greatly increased character sampling would resolve these relationships, a plastome sequence data matrix was assembled for 13 taxa of Apocynaceae, including nine newly generated complete plastomes, one partial new plastome, and three previously reported plastomes, collectively representing all primary crown clade lineages and outgroups. The effects of phylogenetic noise, long-branch attraction, and model selection (linked versus unlinked branch lengths among data partitions) were evaluated in a hypothesis-testing framework based on Shimodaira-Hasegawa tests. Discrimination among alternative crown clade resolutions was affected by all three factors. Exclusion of the noisiest alignment positions and topologies influenced by long-branch attraction resulted in a trichotomy along the spine of the crown clade consisting of Rhabdadenia+the Asian clade, Baisseeae+milkweeds, and Periplocoideae+the New World clade. Parsimony reconstruction on all optimal topologies after noise exclusion unambiguously supports parallel evolution of aggregated pollen in Periplocoideae (tetrads) and milkweeds (pollinia). Our phylogenomic approach has greatly advanced the resolution of one of the most perplexing radiations in Apocynaceae, providing the basis for study of convergent floral morphologies and their adaptive value.